FI85007B - FOERFARANDE FOER FRAMSTAELLNING AV SALTSYRA. - Google Patents

Description

1 85007

The invention relates to a process for the preparation of hydrochloric acid from chlorine and methanol according to the following reaction: CH3OH + 3Cl2 + H2O = 6HCl + CO2 The invention further relates to the use of the hydrochloric acid or hydrochloric acid-methanol mixture thus obtained for the preparation of chlorine dioxide.

The above reaction is known per se, especially from Finnish patent applications 895028, 894901 and 881440, in order to eliminate chlorine formed as a by-product of the reaction in the production of chlorine dioxide. In the process, chlorine formed as a by-product in the production of chlorine dioxide reacts with a reducing agent such as methanol. However, this method 20 is not utilized to prepare hydrochloric acid.

It has now surprisingly been found in the context of the present invention that the yield of the reaction is significantly improved by the action of light. Accordingly, the invention relates to an improvement in the performance of a reaction known per se.

Today, hydrochloric acid is produced by reacting chlorine gas and hydrogen gas in a specially designed hydrochloric acid burner. Since the amount of hydrogen required in the production is large and it is not practical to transport large quantities, the production of hydrochloric acid is practically possible only in the immediate vicinity of a large source of hydrogen, such as a chlorine or chlorate plant. This, in turn, results in high transport costs for salt-35 acid, the usual commercial form of which is a 32% aqueous solution, because more than two-thirds of the load is water. The present invention enables the large-scale production of hydrochloric acid at the site of use of hydrochloric acid without the need for hydrogen gas or special high temperature burners.

In particular, the invention can be utilized in connection with the preparation of chlorine dioxide.

For environmental reasons, efforts are now being made to avoid chlorine dioxide production methods that use sulfur compounds. In such situations, it would be practical to use hydrochloric acid-based methods already on the market, such as ERCO's R5 method, in which chlorine dioxide is prepared from sodium chlorate and hydrochloric acid. However, there are two inconveniences associated with their use: 15 1. The amount of hydrochloric acid required. The reactor, which produces 30 tons of chlorine dioxide per day, uses about 40 tons of 100% hydrochloric acid, i.e. a rich 120 tons of 32% solution per day.

20 2. Chlorine formed as a by-product. Today, for environmental reasons, efforts are being made to reduce the use of chlorine in bleaching, and the above-mentioned 30-tonne chlorine dioxide reactor produces about 20 tonnes of chlorine as a by-product.

25

With the process of the present invention for producing hydrochloric acid, both of the above problems can be solved. The production of 40 tonnes of 100% hydrochloric acid theoretically requires only about 40 tonnes of chlorine and 6 to 30 tonnes of methanol. The chlorine generated as a by-product can be utilized here, so only about 20 tons of fresh chlorine are theoretically needed.

By the process of the invention, hydrochloric acid is prepared by reacting chlorine with aqueous methanol at elevated temperature and allowing light to act on the reaction mixture. Water dilutes the reaction mixture, aids in heat transfer, and hydrolyzes any intermediates.

Il 3 85007

The essential features of the invention are set out in the appended claims.

Figure 1 shows a schematic diagram of the apparatus with which the reaction can be carried out. The equipment recycles the methanol-water solution and feeds the chlorine into the gas space of the tower. This apparatus is hereinafter referred to as the reaction tower and the circulating solution therein as the reaction solution.

10

At normal atmospheric pressure, the HCl content of the reaction solution rises to a level of about 30-35%, after which the hydrochloric acid formed leaves the reaction tower. To recover this hydrochloric acid, an absorption tower 15 is installed downstream of the reaction tower, in which the absorption solution circulates.

The equipment can be operated either batchwise or continuously. In batch operation, the required amount of methanol is charged to the reaction solution circuit and chlorine is fed continuously. The hydrochloric acid content of the reaction solution increases and the methanol content decreases. When the hydrochloric acid content reaches a level of 30-35%, the acid begins to leave the reaction tower in gaseous form, whereupon the concentration of the absorption solution begins to increase. In continuous operation, a methanol-water mixture is continuously fed to the reaction tower, and acid can be removed from the reaction tower continuously.

For further use of hydrochloric acid, it is important to make it as concentrated as possible. In this case, the reaction is carried out by allowing the reaction solution to be concentrated with respect to the hydrochloric acid to such an extent that the hydrochloric acid begins to leave the reaction tower into the absorption tower. Since the methanol in the reaction solution has a vapor pressure, methanol is also removed with the hydrochloric acid, which is also absorbed in the water circulating in the absorption tower. In this case, a solution containing both hydrochloric acid and methanol is obtained from the absorption tower. The methanol content is not detrimental if hydrochloric acid is used to produce chlorine dioxide.

In the process for preparing chlorine dioxide using sodium chlorate as the starting material in the process of U.S. Patent 4,081,520, 4,800,77, methanol is used as a reducing agent in a sulfuric acid solution. In the process of the invention, chlorine dioxide is prepared from sodium chlorate and hydrochloric acid in the presence of a reducing agent. The hydrochloric acid and methanol solution of the process of Figure 1 are used as the hydrochloric acid and reducing agent required in the reaction.

10

In the preparation of chlorine dioxide, hydrochloric acid prepared by the process of the invention can be used, the reaction solution circulating in the reaction tower (removal point A, Fig. 1), which contains methanol in addition to the acid as a reducing agent, or the gaseous hydrochloric acid-methanol mixture leaving the reaction tower (removal point B, Fig. 1) , which can be absorbed into a suitable stream circulating in the chlorine dioxide reactor. In this case, the acid concentration in the chlorine dioxide reactor can be increased, which is advantageous in terms of the course of the reaction. Of course, the hydrochloric acid solution from the absorption tower can also be used as the feed acid for the chlorine dioxide reactor (outlet C, Fig. 1).

It has been found experimentally that in a completely closed apparatus the reaction between chlorine and methanol starts in a fairly good yield when fresh solutions are used, i.e. when there is not yet significant hydrochloric acid in the reaction solution. When the hydrochloric acid content rises to close to 20%, the efficiency decreases. According to the invention, it has surprisingly been found that when light is allowed to act on the reaction mixture, the yield increases significantly and hydrochloric acid concentrations in the reaction mixture of 30% are easily reached.

The following example will further illustrate the invention.

eXAMPLES

Six experiments were performed, in the first four of which the reaction mixture was not exposed to light, and in experiments five and six li 35 5 85007 light were allowed to affect the reaction mixture during the reaction. In all experiments, the temperature was 60-70 ° C, often 63-68 ° C. During the experiment, the heat of reaction generally raised the temperature by about 5 degrees in 7 hours. The results of the experiments are shown in the following 5 tables.

Example 1.

REAKTIOL1UOS

10 Hydrochloric acid Methanol vol./l omp. mBBrB / kg% mBBrB / kg% möarB / kg start 36.00 0.992 35.71 3.55 1.27 12.70 4.54 end 37.00 1.038 38.41 12.50 4.80 10.10 3.88 change 3 · 53 -0.66

ABS0RPTI0LIU0S

Hydrochloric acid Methanol 15 vol./l omp. mBSrB / kg * mBBra / kg * mäflrB / kg start 13.10 0.998 13.07 0.60 0.07 0.98 0.13 end 13.40 1.003 13.44 1.60 0.22 1.52 0.20 change 0.15 0.08 CHLORINE SUPPLY / kg 3.80 is HCl YIELD / kg 3.68 U TE0R YIELD / »94.23 % METHANOL CONSUMPTION 0.58 THEORETIC CONSUMPTION / HCl YIELD 0.64 92.95 THEORETICAL CONSUMPTION / CHLORINE FEED 0.57 98.65 25 Example 2.

REACTION SOLUTION

Hydrochloric acid Methanol vol./l omp. mBBra / kg% weight / kg% weight / kg start 37.00 1.042 38.55 12.70 4.90 9.48 3.65 end 37.00 1.053 38.96 15.20 5.92 7.86 3.06 change 1.03 -0.59 30

ABS0RPTI0LIU0S

Hydrochloric acid Methanol vol./l omp. weight / kg% weight / kg% weight / kg start 13.70 1.005 13.77 1.84 0.25 1.83 0.25 end 13.70 1.010 13.84 3.24 0.45 2.40 0.33 change 0.19 0.08 35 6 85007 CHLORINE SUPPLY / kg 2.00 HCl YIELD / kg 1.22 THEORETICAL YIELD / * 59.34 5 kg * METHANOL CONSUMPTION 0.51 THEORETICAL CONSUMPTION / HC1 YIELD 0.1Θ 34.89 THEORETICAL CONSUMPTION / CHLORINE SUPPLY 0.30 58.79

Example 3.

10 REACTORS

Hydrochloric acid Matanol 1 vol./l omp. amount / kg * amount / kg * amount / kg start 36.00 1.050 37.80 15.00 5.67 11.30 4.27 end 36.00 1.064 38.30 17.80 6.82 9.02 3.46 change 1.15 -0.82

15 ABSORBENT

Hydrochloric acid Methanol vol./l omp. weight / kg% weight / kg% weight / kg start 13.00 1.010 13.13 3.24 0.43 2.40 0.32 end 13.00 1.021 13.27 5.78 0.77 3.71 0.49 change 0.34 0.18 2q CHLORINE FEED / kg 3.00 HCl YIELD / kg 1.49 THEORETICAL YIELD / * 48.29 kg * METHANOL CONSUMPTION 0.64 THEORETICAL CONSUMPTION / HC1 YIELD 0.22 34.14 THEORETICAL CONSUMPTION / CHLORINE SUPPLY 0.45 70.71 25

Example 4.

REACTION SOLUTION

Hydrochloric acid Hetanol vol./l omp. weight / kg * weight / kg * weight / kg start 36.00 1.054 37.94 16.80 6.37 10.80 4.10 end 36.00 1.058 38.09 17.90 6.82 10.40 3.96 30 change 0.44 -0.14 7 85007

the absorption solution

Hydrochloric acid Hetanol1 vol. / 1 omp. mkärk / kg% amount / kg% amount / kg start 13.00 1.021 13.27 5.7Θ 0.77 3.71 0.49 end 13.00 1.026 13.34 6.B5 0.91 4.30 0.57 change 0.15 0.08 5 CHLORINE SUPPLY / kg 1.20 HCl YIELD / kg 0.59 THEORETICAL YIELD / » 47.77 kg% METHANOL CONSUMPTION 0.06 10 THEORETICAL CONSUMPTION / HC1 YIELD 0.09 155.06 THEORETICAL CONSUMPTION / CHLORINE FEED 0.1Θ 324.56

Example 5.

REACTION SOLUTION

Hydrochloric acid Methanol 1 ^ vol./1 omp. amount / kg * amount / kg% amount / kg start 36.00 1.059 38.12 17.60 6.71 11.80 4.60 end 37.00 1.096 40.55 23.40 9.49 8.48 3.44 change 2.78 -1.06

the absorption solution

Hydrochloric acid Methanol »/> vol./l omp. change / kg «mkärk / kg% mBSrä / kg 13.00 1.033 13.43 9.10 1.22 6.46 0.87 lesson 13.40 1.033 13.84 9.34 1.29 6.37 0.88 change 0.07 0.01 CHLORINE SUPPLY / kg 3.60 HCl YIELD / kg 2.85 25 THEORETICAL YIELD /» 76.98 kg »METAN CONSUMPTION 1.05 THEORETICAL CONSUMPTION / HC1 YIELD 0.42 39.92 THEORETICAL CONSUMPTION / CHLORINE SUPPLY 0.54 51.86

The cups in the experiment were allowed to light to affect the reaction solution.

30

Claims (4)

8 85007 Example 6. REACTION SOLUTION Hydrochloric acid Methanol vol. / 1 omp. amount / kg% amount / kg * amount / kg start 37.00 1.090 40.33 22.70 9.15 Θ.40 3.39 end 37.00 1.133 41.92 29.10 12.20 5.44 2.28 ^ change 3.04 -1.11 ABSORPTION SOLUTION Hydrochloric acid Methanol vol./l omp. amount / kg% amount / kg% amount / kg start 13.40 1.033 13.84 9.34 1.29 6.37 0.88 end 13.50 1.041 14.05 11.10 1.56 7.90 1.11 change 0.27 0.23 10 CHLORINE SUPPLY / kg 4.20 HCl YIELD / kg 3.31 OTHERS YIELD /% 76.65 kg% METHANOL CONSUMPTION 0.88 15 TE0R.Consumption / HCl YIELD 0.48 55.19 THEORETIC CONSUMPTION / CHLORINE FEED 0.63 72.00 In this experiment, light was allowed to affect the reaction solution during the reaction. In Experiments 1-4, chlorine was found to pass partially unreacted through the absorption system of Figure 1. In experiments 5 and 6, no chlorine permeation was observed. The chlorine feed rate varied between 7.5 and 10 g / min. In all the experiments, the device was nitrogened at the beginning of the experiment and at the end of the experiment there was some unreacted chlorine in the gas space 25 of the device, which could not be taken into account in the material balance. The catalyzing effect of light is clearly seen as a jump in yield percentage when comparing Experiments 3q 1-4 to Experiments 5 and 6. 9 85007 A process for preparing a hydrochloric acid or hydrochloric acid-methanol solution by reacting chlorine with methanol in the presence of water, characterized in that reaction 5 is carried out at an elevated temperature and the reaction solution in the reaction tower is allowed to be exposed to light. 2. Use of a reaction solution containing hydrochloric acid and methanol to prepare chlorine dioxide from sodium chlorate in the presence of a reducing agent, which reaction solution is prepared by reacting chlorine with methanol in the presence of water at elevated temperature and allowing light to act on the reaction solution. Use according to Claim 2, characterized in that the hydrochloric acid / methanol vapor mixture leaving the reaction tower is used as the hydrochloric acid and the reducing agent used in the reaction. Use according to Claim 2, characterized in that a hydrochloric acid / methanol-water mixture absorbed in water is used as the hydrochloric acid and the reducing agent used in the reaction.